Indole 3 acetic acid. Synonyms 5- fluoro UR- 144 5-FUR-144 XLR11 (exempt preparation) indole 3 acetic acid is an analytical reference standard characterized as a?synthetic cannabinoid. 1 ?XLR11 is regulated as a Schedule I compound in the United States. XLR11 (exempt preparation) (Item No. 15033) is provided as a DEA exempt preparation. This?product is intended?for research and forensic applications. 1H indol 3 yl.